package org.example
import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.functions.desc
import org.apache.spark.sql.types.{IntegerType, StringType, StructField, StructType}
object SQL2{
  def main(args: Array[String]): Unit = {
    //创建spark运行环境
    val spark = SparkSession
      .builder()
      .master("local[*]")
      .appName("spark")
      .getOrCreate()
    val sc = spark.sparkContext
    //表结构读取电影用户数据
    val schemaUser = StructType(Seq(
      StructField("id", IntegerType),
      StructField("gender", StringType),
      StructField("age", IntegerType),
      StructField("occupation", IntegerType),
      StructField("location", StringType),
    ))
    val user = spark.read.option("sep","::").schema(schemaUser)
      .csv("src/main/resources/users.dat")
    user.show(5)
    //1.查询替换 where/filter
    user.where("gender = 'F' and age = 18").show(3)
    user.filter("gender = 'F' and age = 18").show(3)

    spark.udf.register("replace",(x:String) =>{
      x match {
        case "M" => 0
        case  "F" => 1
      }
    })
    user.selectExpr("id","replace(gender) as sexual","age").show(3)
    user.select("id","age","location").show(3)

    //2.排序orderBy sort
    user.orderBy(desc("age")).show(5)
    user.sort(-user("id")).show(5)
    //3.分组
    user.groupBy("gender").count().show(5)
    //4.连接join(DataFrame,"列名","连接方式left_outer“)
    //5.练习：求18岁女生评分电影为5分的所有电影名
    val schemaRatings = StructType(Seq(
      StructField("user_id", IntegerType),
      StructField("movie_id", IntegerType),
      StructField("rating", IntegerType),
      StructField("timestamp", IntegerType)
    ))
    val ratings = spark.read.option("sep", "::").schema(schemaRatings)
      .csv("src/main/resources/ratings.dat")
    val schemaMovies = StructType(Seq(
      StructField("movie_id", IntegerType),
      StructField("title", StringType),
      StructField("genres", StringType)
    ))
    val movies = spark.read.option("sep", "::").schema(schemaMovies)
      .csv("src/main/resources/movies.dat")
    val result = user
      .join(ratings, user("id") === ratings("user_id"))
      .join(movies, ratings("movie_id") === movies("movie_id"))
      .filter("gender = 'F' AND age = 18 AND rating = 5")
      .select("title")
      .distinct()
    result.show()
    sc.stop()
  }
}